1. Field of the Invention
The present invention relates generally to wafer preparation belts, and more specifically to the fabrication of belt materials used in chemical mechanical planarization apparatus.
2. Description of the Related Art
In the fabrication of semiconductor devices, a plurality of layers are typically disposed over a substrate, and features are defined in and through the layers. A surface topography of the substrate or wafer can become irregular during fabrication processes, and an un-corrected irregularity increases with the addition of subsequent layers. Chemical Mechanical Planarization (CMP) has developed as a fabrication process utilized to planarize the surface of a semiconductor wafer, as well as to perform additional fabrication processes including polishing, buffing, substrate cleaning, etching processes, and the like.
In general, CMP processes involve the application of a substrate or wafer against a processing surface with a controlled pressure. Both the processing surface and the wafer are caused to rotate, spin, or otherwise move independently of one another to create a frictional force for planarization and to ensure the entire surface of the wafer is consistently and controllably processed. Typical CMP apparatus include linear belt processing systems in which a belt having a processing surface is supported between two or more drums or rollers which move the belt through a rotary path presenting a flat processing surface against which the wafer is applied. The wafer is typically supported and rotated by a wafer carrier, and a polishing platen is configured on the underside of the belt traveling in its circular path. The platen provides a stable surface over which the belt travels, and the wafer is applied to the processing surface of the belt against the stable surface provided by the platen. In some applications, abrasives in an aqueous solution known as slurry are introduced to facilitate and enhance the planarization or other CMP process.
Additional CMP apparatus include rotary CMP processing tools having a circular pad configuration for the processing surface, an orbital CMP processing tool similar to the circular CMP processing tool, a sub-aperture CMP processing tool, and other CMP processing systems providing a plurality of apparatus and configurations that, in general, utilize chemical and mechanical forces to planarize, scrub, polish, buff, clean, or otherwise process the surface of a semiconductor wafer having integrated circuits or other structures fabricated thereon.
In the linear belt CMP system, the belt and processing surface are typically fabricated to provide a stable structure to withstand the stresses of the belt and drum configuration, as well as a stable processing surface upon which precise and controllable planarization can occur. In addition to the stretching and contraction caused by the belt and processing surface traveling around the drums that drive the system, the belt and processing surface are typically in a wet environment from the liquid from slurry and rinsing operations. Belts and processing surfaces are typically constructed of a plurality of materials such as, by way of example, a stainless steel supporting layer, a cushioning layer, and one or more processing surface layers. The plurality of layers are joined by adhesives, bonding, stitching, and the like to form the continuous belt structure with an outwardly facing processing surface against which a wafer is applied in a CMP process.
The fabrication of linear belts in a plurality of layers as described provides the necessary support to substantially prevent the stretching of linear CMP belts, but adds manufacturing costs to belt construction, such belts can be difficult to work with, and such belts are subject to structural failure at openings for end point detection systems, and due to break down of the bond between layers caused by normal use and aggravated by the typically wet CMP environment.
Other examples of linear CMP belts include substantially polymer material without the additional layers described above, but the substantially polymer material belts tend to stretch and otherwise deform with continued use. Woven fabric has been added to some belts for rigidity, but woven fabric also allows some measure of stretch, can be difficult to work with, and does not provide for discontinuities in the fabric for end point detection openings without unraveling of the fabric if the discontinuities are fabricated prior to belt casting. If the discontinuities are desired to be fabricated in a woven fabric after casting, considerable time, effort, and expense are required to create the openings in a completed reinforced belt. Additionally, fabric is difficult to work with in belt casting, and lacking rigid structure or form, is difficult to position for fabrication.
Linear belts used in linear belt CMP systems can be costly to manufacture, and can be time consuming to replace. Replacement of linear belts requires down time for the CMP system resulting in decreased through put and increased manufacturing costs. Linear belts can be subject to such failures as delamination or separation of the layers due to such factors as the contraction and stretching forces during use, and the breakdown of adhesives or other bonding techniques over time and accelerated in the wet CMP environment.
In view of the foregoing, what is needed are methods, processes, and apparatus to fabricate a linear CMP processing belt that is resilient to the stresses of use, less likely to delaminate or otherwise separate, and economical and easy to manufacture.
Broadly speaking, the present invention fills these needs by providing a reinforced polymeric CMP processing belt having an inner mesh core. The present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method. Several embodiments of the present invention are described below.
In one embodiment, a processing belt for use in chemical mechanical planarization (CMP) is disclosed. The processing belt includes a mesh belt and a polymeric material encasing the mesh belt to define the processing belt to be used in CMP operations.
In another embodiment, a belt for use in chemical mechanical planarization (CMP) processing is disclosed. The belt includes a polymeric material being cast into a continuous loop to define the belt, and a continuous mesh core embedded in the polymeric material. The continuous mesh core is defined as a more rigid inner core of the polymeric material.
In still a further embodiment, a processing belt for use in chemical mechanical planarization (CMP) is disclosed. The processing belt includes a continuous loop reinforcing mesh and a polymeric material. The polymeric material encases the reinforcing mesh to define the processing belt to be used in CMP operations. The continuous loop reinforcing mesh is constructed of stainless steel as a matrix of intersecting members bonded at joints to form a rigid mesh structure.
In yet another embodiment, a method for fabricating a belt for use in chemical mechanical planarization (CMP) is disclosed. The method includes forming a belt-shaped mesh, and providing a mold configured to form a belt-shaped structure. The belt-shaped mesh is positioned in the mold and a polymeric material is formed in the mold. The polymeric material is formed around and through the belt-shaped mesh such that the belt-shaped mesh is encased in the polymeric material.
In an additional embodiment, a method for fabricating a belt for use in chemical mechanical planarization (CMP) is disclosed. The method includes forming a belt-shaped mesh. A mold is provided that is configured to form a belt-shaped structure. A first polymeric material is formed in the mold. The first polymeric material is formed within the mold to define a polymeric belt. The first polymeric material is then cured, and the belt-shaped mesh is positioned against an interior surface of the polymeric belt. A second polymeric material is applied around and through the belt-shaped mesh such that the belt-shaped mesh is encased between the first polymeric material and the second polymeric material. The first polymeric material and the second polymeric material are chemically bonded together.
The advantages of the present invention are numerous. One notable benefit and advantage of the invention is significantly increased lifetime of the polymeric CMP processing belt in the CMP process. Unlike a typical linear CMP processing belt of prior art, the inner mesh core of the present invention provides the necessary strength, support, and resilience without stacks of bonded layers subject to delamination or separation. The inner mesh core of the present invention is encased within the structure of the processing belt and is therefore integral to the belt structure. Polymeric material is cast around and through the inner mesh core, or sprayed over and through the inner mesh core, resulting in a CMP processing belt of significantly increased lifetime in the CMP process.
Another benefit is the lower cost and ease of manufacture. Unlike typical prior art processing belts, the present invention includes a single inner mesh core around which the polymeric mass of the polishing belt is cast. The plurality of layers, adhesives, stitches, or other bonding materials between the plurality of layers are eliminated without compromise of strength, support, and resilience.
An additional benefit is the ability to readily integrate embodiments of the present invention with optical end point detection apparatus. The inner mesh core of the present invention provides for easy fabrication of optical xe2x80x9cwindowsxe2x80x9d for use with end point detection apparatus, and without compromise of necessary strength, support, and resilience. Further, integration of optical end point detection structures does not increase the likelihood of delamination or separation, or decrease the useable life of the processing belt.
Yet another advantage and benefit is the plurality of options provided by the present invention for specific or specialty applications. Embodiments of the present invention can be easily implemented with preferential reinforcement according to specific circumstance or desired use.